Sticky tape emits x-rays

Wired posted a gallery covering an interesting phenomenon. When you unroll regular sticky tape it emits visible light, but what was recently discovered is that under vacuum it actually emits x-rays as well. They’re still trying to nail down the cause. Have a look at the gallery of UCLA’s research lab to see what kind of equipment you need to unroll tape in a vacuum.

when you pull some materials apart you create electrical charges. x-rays are a form of electromagnetic radiation and have a shorter wavelength then visible light. my guess is the tape is forming an electrical charge when pulled apart and somehow the light is being “filtered” by this electrical charge. this is just my two cents so don’t go ballistic on me. oh hell, you will anyway i don’t care.

As a field tech in the electrical industry, I have worked on switches that use vacuum bottles to extinguish the arc of high voltage switching. The manufacturers warn against subjecting the vacuum equipment to voltages higher than they were designed to handle, because they will emit x-rays in this overvoltage condition. I am not an expert, so I cannot say why, but it seems like high voltage + vacuum = x-rays is not that unusual.

The group believes that as the tape peels the acrylic adhesive on the exposed tape becomes positively charged and the outer surface of the remaining polyethylene roll acquires a negative charge. This causes electric fields to build up to values that trigger discharges.

The researchers say that at the reduced pressure in the experiment — about one millionth of an atmosphere — the discharges accelerate the electrons to energies that generate X–rays when they suddenly decelerate in the positive side of the tape.

Yesterday i see this phenomen when open letter, carefully separating glued sides in the dark and i think what a f**k. Thanks Hack a day now i know hapens:) But when i try this with another letter nothing hapens :( Maybe this hapens with some special glues?

i notice that they are showing that they are using a small roll of tape, maybe 1 inch across, i got a big roll of similar packaging tape at home for sealing up cardboard boxes, its around 3.5 inches across and in the dark it glows kinda bright, brighter as the speed increases. its a little disconcerting to know that when i use tape i create a discharge that contains x-rays/other rays. i hope that if you monkey around with tape a lot you don’t accidentally get radiation sickness. just think of the lawsuits that are on the way. i wonder if the manufactures were aware of this unique byproduct before it hit the public.

A typical method of producing x-rays is to heat a tungsten filament in a vacuum. The elevated temperature causes electrons to be discharged into a vacuum. It’s called the thermionic effect.

The discharge of photons from unrolling tape has been a known phenomenon for quite some time (I played with it as a kid too). It’s fascinating that this can produce high energy photons though. According to the article on ScienceNews.org, “At normal atmospheric pressure, the electrons are slowed down by air particles, so they never reach the speeds and energies required for making X-rays.” This I had expected was part of the reason. The tape is always emitting electrons, but the atmosphere slows them down.

The other part (my own hypothesis), not mentioned, is the fact that the friction of pulling tape off of a roll actually can create noticable wasted heat energy. I’ve used a lot of tape in a very short time and the roll can become quite warm. This additional heat energy may be contributing to the thermionic effect at lower temperatures than are needed normally. It is also possible that the airborn particles of adhesive (identifiable by smell) may serve as accidental lasing medium or form excimers that become excited in the presence of the emitted electrons. I’m going out on a limb, but it’s the best I can do since they can’t explain the effect themselves.

The mechanism that generates the high voltage is due to the conservation of charge, q, and the relationship q=cv.

When the tape is peeled off the capacitance between the layers is suddenly reduced to a tiny fraction so the voltage shoots up until there is a discharge. I would expect a lot more voltage in a vacuume with no gas to ionise and discharge the capacitance.

X-Rays are not formed by the *acceleration* of electrons, but rather the sudden stop when very fast electrons hit a target, normally metallic, causing secondary x-ray emission.

For perspective, a friend has a power supply from a medical x-ray machine, an oil-filled tank about 1.5 ft cube with huge HV bushings on top, rated at truly lethal 100kV at ~100mA (short duty-cycle). Because of this sort of power level some x-ray tubes have rotating targets so they don’t melt.

Very little risk of radiation sickness from sticky tape I think, even in space. :)

I bet there are much better materials out there then regular office tape. Can you imagine portable x-ray machines, machines that won’t need power because you could peddle them to generate x-rays. I’m really interested in scientific discoveries like this one hackaday, keep up the great posts.

At one point in the video the experimenter holding the radiation meter says that he’s getting scared, so this setup may in fact generate quite a lot of radiations, more than I’d have guessed. There is apparently enough x-rays emitted to make a radiography of a finger.